The present invention relates to the preparation of conjugated dienes by dehydration of aliphatic aldehydes and more particularly to the dehydration of 2-methylbutanal to obtain isoprene.
It is known that conjugated dienes can be obtained from the corresponding aliphatic aldehyde having the same number of carbon atoms by contacting the aldehyde with an acidic dehydration catalyst. Examples of suitable acid dehydration catalysts include inorganic acids such as phosphoric acid, boric acid, silicic acid and titanic acid. Other suitable acidic dehydration catalysts include the salts of the above-described acids and acid anhydrides having a latent acid function. While use of the above-described catalysts to dehydrate aldehydes to conjugated dienes is known, embodiments of this process reported heretofore have been substantially impeded by catalyst deactivation with attendant loss of selectivity after as short a period as thirty minutes, see British Pat. No. 1,385,348.
It is therefore the overall object of the present invention to provide an improved process for the dehydration of aliphatic aldehydes to obtain the corresponding conjugated diene.
Accordingly, it is an object of the present invention to provide an improved process having prolonged catalyst activity.
It is yet another object of the present invention to provide an improved process having sustained catalyst selectivity versus reaction time.
These and other objects, features and advantages of the present invention will be evident to those skilled in the art from the following description.